Replace JoinNetworkViewController with obj-c

ZeroTier One/JoinNetworkViewController.h

@@ -0,0 +1,27 @@
+//
+//  JoinNetworkViewController.h
+//  ZeroTier One
+//
+//  Created by Grant Limberg on 8/7/16.
+//  Copyright © 2016 ZeroTier, Inc. All rights reserved.
+//
+
+#import <Cocoa/Cocoa.h>
+
+
+extern NSString * const JoinedNetworksKey;
+
+@interface JoinNetworkViewController : NSViewController <NSComboBoxDelegate, NSComboBoxDataSource>
+
+@property (nonatomic, weak) IBOutlet NSComboBox *network;
+@property (nonatomic, weak) IBOutlet NSButton *joinButton;
+@property (nonatomic, weak) IBOutlet NSButton *allowManagedCheckBox;
+@property (nonatomic, weak) IBOutlet NSButton *allowGlobalCheckBox;
+@property (nonatomic, weak) IBOutlet NSButton *allowDefaultCheckBox;
+
+@property (nonatomic) NSMutableArray<NSString*> *values;
+
+- (IBAction)onJoinClicked:(id)sender;
+
+
+@end